Till recently, various strategies have been tried in the field of education as far as mastering the study material by school children is concerned. In fact, it has been a topic of interest for many years. Today, Computer Based Mastery Learning is considered as one of the most effective means of attaining mastery learning. To explore the effectiveness of Computer based Mastery Learning Strategy on achievement in Chemistry of IX graders in relation to Academic Stress and Parental Involvement, a school sample of two hundred and forty 9^th grade students of high and low Parental Involvement and Academic Stress was drawn from the representative Secondary Schools of Chandigarh. The major findings of the study were:

• The mean gain in Chemistry through Computer Based Mastery Learning was more than the mean gain through Conventional Group Learning.
• The gain means in Chemistry of the two Parental Involvement groups (High & Low) may not be treated as different beyond the contribution of chance factor and the observed mean difference may be ascribed to the chance factor alone.
• The gain means in Chemistry of the two groups (High and Low Academic Stress) may not be treated as different beyond the contribution of chance factor and the observed mean difference may be ascribed to the chance factor alone.
• The two variables Instructional Strategies (CBML&CGL) and Parental Involvement (High & Low) do not interact to yield difference in gain means in Chemistry and the two variables act independent of each other.
• The two variables Instructional Strategies (CBML&CGL) and Academic Stress (High & Low) do not interact to yield difference in gain means in Chemistry and two variables act independent of each other.
• The two variables parental Involvement (High & Low) and Academic Stress (High & Low) do not interact to yield difference in gain means in Chemistry and may be taken as independent of each other.
• The three variables Instructional Strategies, parental Involvement and Academic Stress interact with each other to yield differences in gain means in Chemistry for different combination groups:
• Students with High Parental Involvement and High Academic Stress attained higher gain means in chemistry through Computer Based Mastery Learning than through Conventional Group Learning.
• Students with High Parental Involvement and Low Academic Stress attained higher gain means through Computer based Mastery Learning than those with High Parental Involvement and Low Academic Stress studying through Conventional Group Learning.
• Students with Low Parental Involvement and High Academic Stress achieved higher gain means through Computer based Mastery Learning than those with Low Parental Involvement and High Academic Stress who were studying through Conventional Group Learning.
• Students with Low Parental Involvement and Low Academic Stress achieved higher gain means through Computer based Mastery Learning than those with Low Parental Involvement and Low Academic Stress who were studying through Conventional Group Learning.
• Students of Computer based Mastery Learning group with High Parental Involvement and with High Academic Stress achieved equal gain means in Chemistry as those with High Parental Involvement and Low Academic Stress studying through Computer based Mastery Learning.
• Conventional Group Learning students with High Parental Involvement having High Academic Stress attained equal gain means in Chemistry as those of Conventional Group Learning group having High Parental Involvement and Low Academic Stress.
• Computer based mastery learning group with Low Parental Involvement and High Academic Stress achieved equal gain means in Chemistry as Computer based mastery learning group with Low Parental Involvement and low Academic Stress group.
• Conventional Group Learning students with Low Parental Involvement and High Academic Stress are not different on their achievement gain means in Chemistry from their counterparts of Conventional Group Learning and Low Parental Involvement with Low Academic Stress.
• Students within Computer based mastery learning group with High Academic Stress; High Parental involvement group achieved equal gain means as those with Low Parental Involvement.
• Within Computer Based Mastery Learning group and Low Academic Stress, students with High Parental Involvement achieved equal gain means in Chemistry as those within similar group having low parental involvement.
• Students of Conventional Learning Group with High Parental Involvement and with High Academic Stress achieved equal gain means as those with Low Parental Involvement and High Academic Stress studying through Conventional Group Learning.
• Within Conventional Group Learning with Low Academic Stress; students with High Parental Involvement and those in Low Parental Involvement group achieved equal gain means in Chemistry.